Sweat electrolytes test

A colorless, odorless chemical that causes sweating is applied to a small area on an arm or leg. An electrode is then attached to the spot. A weak electrical current is sent to the area to stimulate sweating. People may feel a tingling in the area, or a feeling of warmth. This part of the procedure lasts for about 5…

No special steps are needed before this test.

The test is not painful. Some people have a tingling feeling at the site of the electrode. This feeling may cause discomfort in small children.

Sweat testing is the standard method for diagnosing cystic fibrosis. People with cystic fibrosis have higher amounts of sodium and chloride in their sweat that are detected by the test. Some people are tested because of symptoms they are having. In the United States, newborn screening programs test for cystic…

Normal results include: A sweat chloride test result of less than 30 mmol/L in all populations means cystic fibrosis is less likely. A result between 30 to 59 mmol/L does not give a clear diagnosis. Further testing is needed. If the result is 60 mmol/L or greater, cystic fibrosis is present. Note: mmol/L = millimole…

An abnormal test may mean that the child has cystic fibrosis. Results can also be confirmed by CF gene mutation panel testing.

Egan ME, Schechter MS, Voynow JA. Cystic fibrosis. In: Kliegman RM, St. Geme JW, Blum NJ, Shah SS, Tasker RC, Wilson KM, eds. Nelson Textbook of Pediatrics . 21st ed. Philadelphia, PA: Elsevier; 2020:chap 432. Farrell PM, White TB, Ren CL, et al. Diagnosis of cystic fibrosis: consensus guidelines from the Cystic…